The present invention relates to pumps, and more particularly to improvements in reciprocating linear pumps. The linear pump of the present invention is relatively simple and thus inexpensive to manufacture and maintain, yet has a surprisingly high pump efficiency. The pump of the present invention is particularly well suited for pumping blood intracorporeal or extra-corporeal bridge to a transplant or a total cardiac replacement. The pump may alternatively be used to pump sewage or wastewater, or may be used in other industrial, commercial, medical, astronautical, aeronautical, or military applications.
Pumps have been used for centuries, and various types of pumps have been devised, including positive displacement pumps, rotary pumps, vane pumps, and centrifugal pumps. While many of these pumps are well suited for particular uses, pumps in general do not have a high efficiency, and are not well suited for special applications, such as pumping blood or pumping sewage wastewater.
Current pumps include the crew of Archimedes that interferes with axial blood flow. Many pumps cause damage to the blood components as these blood components make either direct or near contact that surfaces of the pump. Ventricular assist pumps currently employ mechanisms to move blood that stresses the blood in some situations and are non-pulsatile.
When pumping blood, constant flow by conventional pumps may cause xe2x80x9cpumpheadxe2x80x9d because of the sustained vasiodilation. The alterations in the cellular components of the blood, typical with rotary and constant flow pumps, may be due to reactions with the vasodialted capillaries and the components of the blood reacting to this abnormal state. Ischemia may be present to the decreased lumen secondary to an accumulation of platelets and/or the blood not pulsing enough to create turbulence and transfer the gases and nutrients. This would thus be analogous to going too fast by a road sign. It may be due to the hemodynamics of fluid flow with a non-newtonian fluid. The pulse flow preferably allows for a psychological pause in the short duration dilated phase and the contraction may facilitate the movement of the blood components.
Various types of linear pumps have been devised, including linear pumps particularly intended for pumping blood. U.S. Pat. Nos. 5,676,162 and 5,879,375 disclose reciprocating pump and linear motor arrangements for pumping blood. The assembly includes a piston-valve which is placed at the inlet end of a hollow chamber. The valve leaflets may be in any arbitrary position. The pump module arrangement may occupy a space of no more than approximately 6 cm. in diameter and 7.5 cm. long. In a preferred embodiment, a quick connect locking system may be utilized, as shown in FIG. 3 of the ""162 Patent. FIG. 11 of the ""375 Patent illustrates the anatomical arrangement of a surgically implantable pump with a reciprocating piston-valve. Other patents directed to implantable pumps and or linear pumps include U.S. Pat. Nos. 5,676,651, 5,693,091, 5,722,930, and 5,758,666.
Conventional pumps have long been used to pump a slurry consisting of a fluid and a semi-solid material, which is common in sewage wastewater. Conventional wastewater pumps have significant problems due to pump plugging and abrasion, which increases repair and maintenance costs, and results in poor pump efficiency and/or short pump life.
The disadvantages of the prior art are either overcome or are reduced by the present invention, and improved linear pumps and methods of pumping fluids are hereinafter disclosed which overcome many of the disadvantages of prior art pumps, including relatively high cost of manufacture and/or poor pump efficiency.
The present invention is directed to highly versatile linear pumps. In one embodiment the pump may be used for pumping blood through a living body, and it may include a pump housing having a non-oxygenated blood inlet, a non-oxygenated blood outlet, an oxygenated blood inlet, and an oxygenated blood outlet. The pump may include both a non-oxygenated bladder and an oxygenated bladder each for receiving and for outputting blood at a desired pulse rate. The pump may further include a non-oxygenated blood inlet check valve, a non-oxygenated outlet check valve, an oxygenated blood inlet check valve, and an oxygenated blood outlet check valve for passing the blood through the pump. An inlet plate and an outlet plate may be secured to corresponding ends of each of the two bladders. The pump includes a prime mover for linearly moving an inlet plate secured to a respective bladder with respect to an outlet plate secured to the same bladder such that linear movement of the inlet plate with respect to the outlet plate alters the volume within the bladder to pump the blood. A control member is provided for controlling linear movement of the end plates and thereby controlling the first pulse rate and the second pulse rate caused by the pumping action of the first bladder and the second bladder, respectively. The pump flow for the decreased demand of the right ventricle may be accommodated by pump size, output, bladder size, or stroke volume.
The pump may be used extra-corporeal as a single unit to move blood through the inner chamber and a lubricant/thermal fluid through the outer chamber to maintain a comfortable state for the patient treated. The fluid that is passed through the outer chamber may be such to facilitate components to be moved through a selectively permeable inner bladder. This use is in a dialysis-like setting. Another embodiment only utilizes the inner chamber for fluid movement to realize the benefit of the parastalyic movement.
In still another embodiment, the pump may assist the heart as a left ventricular assist device with configuration and attachment such as is found in the Heart Mate II LVAS. In yet another embodiment, the pump is used as a wastewater pump and includes a housing having a throughbore about a central axis, an incoming end cap and outflowing end cap, a flexible generally tubular bladder defining an inner chamber and an outer chamber, an incoming inner chamber check valve, an outflowing inner chamber check valve, at least one incoming outer chamber check valve, at least one outflowing outer chamber check valve, and a power supply with electronics for controlling the attraction and repulsion of the end caps to cyclically move one end cap with respect to the other end cap along a central axis in a manner which cyclically varies the volume of both the inner chamber and the outer chamber, thereby creating propulsion forces and pumping the wastewater.
The pump according to the present invention may utilize magnetic propulsion and contraction forces to change the length and thus the internal volume within a flexible bladder, which may be reinforced with a weave comprising fibrous reinforcing members. In an alternate embodiment, hydraulic power to cylinders is controlled to effect movement of the end caps and thereby cyclically change the volume of the inner chamber and the outer chamber which are separated by the bladder. Volume changes within the bladder and in many applications between the bladder and the external housing may be used to generate the pumping forces.
To create compressive forces to move fluid, the pump may utilize one or more inner chambers and corresponding outer chambers which may each contribute to the pumping of fluid. The pump according to the present invention thus may fill an outer chamber with fluid as the inner chamber is venting, then fill the inner chamber with fluid while the outer chamber is venting. This feature minimizes the pressure differential, which decreases the work and thus the effort needed for the pump.
In one embodiment, the pump is used as a blood pump and two bladders are provided, preferably with counter offset check valves to ideally balance the pump operation with due concern to output demands. For this embodiment, the chamber exterior of the bladders may be vented to atmosphere, or alternatively may be provided with another desired fluid.
In an another embodiment, the pump is used as a wastewater pump, and in that case preferably the chamber exterior to the bladder is sealed within the housing, such that the bladder creates both an inner chamber and an outer chamber. The wastewater fluid flows through each chamber to efficiently pump wastewater. In one embodiment, the bladder itself may be permeable such that relatively clean wastewater passes from within the bladder radially outward to the outer chamber, thereby contributing to the volume of relatively clean wastewater in the outer chamber and thus minimizing the volume of relatively dirty wastewater which must be treated in a manner more costly than the relatively clean wastewater. The proportion of the pump will vary with the rate of transfer through the walls.
It is a feature of the invention that the pump may utilize valves which include polymer reeds that are in a tricuspid and/or bicuspid configuration similar to that of a human heart valve. Each valve in the device may be sized analogous to cardiac portions in the heart valve. The valves preferably are self-cleaning and quiet, and also have high efficiency and longevity.
It is a further feature of the invention that the material which provides the helix reinforcement may be formed of a carbon fiber, an aromatic polyamide fiber such as Kevlar, or currently advanced reinforcement which has significantly better fatigue properties than metal wire.
It is another feature of the invention that when the pump is used as a wastewater pump, the bladder may be permeable such that relatively wastewater may pass from the interior of the bladder through the bladder and to the exterior of the bladder, thereby minimizing the volume of relatively dirty wastewater which must be treated.
It is a further feature of the invention that the end caps may be both configured and provided with a suitable sealing member for obtaining a reliable fluid tight seal between both the stationary and the movable end caps, whether that seal be made with blood vessels, a wastewater pipeline, or other fluid conduit.
In another embodiment, the pump may be used to move fluids necessary to operate machinery and equipment to include, but not limited to, submarines, boats, airplanes, aerospace and spacecraft. Due to the minimal size, weight, and parts, the pump may allow for an increased payload.
Another feature of the invention is that the pump utilizes moving parts that are forgiving.
The pump according to the present invention is highly versatile; the length of the pump stroke may be complete or partial.
A further feature of the invention is that the pump may utilize attracting and repelling end caps and conventional sealing members, such as o-rings with reduced friction, to form reliable seals within the device.
It is a further feature of the invention that the end caps may be provided with a TEFLON(trademark) coating. Alternatively, the end caps may be coated with a fine diamond material to create a very low friction surface for sealing between the movable end cap and the housing.
Yet another feature of the invention is that the pump may be electrically powered to change the magnetic attraction and repulsion of the end caps, or may be hydraulically powered to serve this same purpose.
An advantage of the invention is that the pump is relatively simple and thus highly reliable. The further advantage of the invention is that the pump may provide a relatively long life with few service problems.
These and further objects, features, and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.